1. Field of the Invention
The present invention generally relates to a liquid toner composition and a preparation method of the same. More specifically, the present invention relates to a liquid toner composition including an organosol whose dispersion assistant agent has an unsaturated double bond subjected to photopolymerization and a photoreactive catalyst for initiating the photopolymerization of the dispersion assistant agent to facilitate hardening of toner particles transferred onto a recording medium, consequently improving an overall print quality.
2. Description of the Related Art
A liquid toner composition is widely used for electrophotographic image forming apparatuses, such as, copiers, laser printers, and fax machines. These electrophotographic image forming apparatuses use electrically charged toner particles to print a desired image onto a recording medium.
There are two types of electrophotographic image forming apparatuses. One type includes the dry electrophotographic image forming apparatuses that use a dry toner, and the other type includes wet electrophotographic image forming apparatuses that use a liquid toner. The liquid toner, as compared with the dry toner, uses micro-fine toner particles, so that it features high resolution and high print speed. Moreover, the wet electrophotographic image forming apparatus uses a relatively smaller amount of toner and thus, the replacement period of the toner may be extended.
The liquid toner is prepared by dispersing toner particles onto an aqueous carrier. More specifically, a liquid carrier consists of toner particles including a colorant and a polymer as a binder resin, a charge control agent for controlling the charge on a toner particle, a liquid carrier wherein toner particles and the charge control agent are dispersed, and an optional additive for improving the performance of the toner.
FIG. 1 is a schematic diagram of a conventional wet electrophotographic image forming apparatus. A laser scanning unit (not shown) scans a laser beam onto each photosensitive drum 10 in the direction the arrow is pointing. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 10. Next, a toner inside a developer 50 comes in contact with the photosensitive drums to generate a visible image on the surfaces of the photosensitive drums. The image is transferred to an intermediate transfer belt 30. The image transferred to the transfer belt 30 passes through a fixing roller 60, and is fixed onto the recording medium as a permanent image.
According to the kind of binder resin used, the liquid toner for use in the wet electrophotographic image forming apparatus is generally divided into a liquid toner using a common resin, and an organosol toner using an organosol.
The toner organosol includes 0.1-10 micron diameter toner particles that are stably charged. Thus, high resolution images may be achieved.
However, a percentage of weight occupied by a carrier liquid in a conventional toner organosol is relatively high, so solid components in the toner often aggregate again, and this tendency makes it difficult to store the toner organosol at a high temperature for an extended period of time. To solve this problem, a liquid toner including a dispersion assistant agent has been developed, under the condition that the optical density (OD) of a printed image is maintained at a predetermined level. As for the dispersion assistant agent, a polymer material soluble in the liquid carrier has generally been used. Particularly, the most preferred material for the dispersion assistant agent is the (metha)acrylate (co)polymer because it rarely affects the liquid toner's own physical properties, but may improve the storage stability for an extended period of time.
However, the (metha)acrylate (co)polymer has a high viscosity. Therefore, when the (metha)acrylate (co)polymer is transferred onto the recording medium with other ingredients of the liquid toner, it adheres to the fixing roller as the recording medium passes through the fixing roller. Since parts of the toner particles remain and are not transferred onto the recording medium, the resolution of the finally fixed image on the recording medium deteriorates, and the printed portion is easily erased.
The (metha)acrylate (co)polymer adhered to the fixing roller continues to influence the printing operation later on, and deteriorates the print quality.